Apr 12, 2013

Last night at HSB we had a JTAG finder workshop, during which we quickly hacked together a JTAG scanner for the ATmega328, called Arduinull (it’s not a port of Hunz’s JTAG finder as we initially planned to do). It is compatible with Arduino Duemilanove, so that people from low-standard DIY websites for the masses will see it and go “wow!”.

gizDuino mini variant with USBaspLoader firmware and USB programming port to form a complete low cost Arduino compatible mini board! No need for a separate USB programmer. Choice of ATMEGA328 or ATMEGA168 controller.

You can download the files here. They are public domain ; copyright is irrelevant on such a trivial piece of software. It tries every JTAG pinout on the 6-pin port C of the microcontroller analog input connector of the Arduino, shifts a pattern into the IR chain and tries to read it back. Add protective 330 ohm resistors in series with your device.

A possible improvement would be to add a relay controlled by the AVR microcontroller Arduino to power-cycle the device, in case the JTAG chip gets confused. Also, it should detect the IR length and reject a length of zero which is more likely due to two pins connected together.